#define _CRT_SECURE_NO_WARNINGS 1
#include<bits/stdc++.h>
using namespace std;
const int N = 110;
int a[N], b[N];
bool cmp(int x, int y) {
    return x > y;
}
int main() {
    int n, m, x; cin >> n >> m >> x;
    for (int i = 1; i <= n; i++) cin >> a[i];
    for (int i = 1; i <= m; i++) cin >> b[i];
    sort(a + 1, a + n + 1, cmp);
    sort(b + 1, b + m + 1, cmp);
    if (x - b[1] < 1) {
        cout << 1 << endl;
        return 0;
    }
    int cnt = 0, f = 0;
    for (int i = 1; i <= m; i++) {
        if (x - b[i] < 1) {
            cnt++; f = 1; break;
        }
        else {
            x -= a[i] * b[i];
            cnt += 2;
            if (x < 1) {
                f = 1; break;
            }
        }
    }
    if (f) cout << cnt << endl;
    else cout << -1 << endl;
    return 0;
}